The long-term objective of this project is to determine the roles of the enzyme cytosolic phospholipase A2 alpha (cPLA2a) in the evolution of injury following stroke. cPLA2a catalyzes the intracellular release of arachidonic acid from membranes. Cerebral ischemia-reperfusion activates phospholipase A2 resulting in increased levels of arachidonic acid and its eicosanoid metabolites. We showed that cPLA2a-deficient mice suffer significantly less neuronal injury after focal cerebral ischemia/reperfusion. We have now identified KIDS- cPLA2a, a novel form of cPLA2a, which is specifically induced in the dentate gyrus and protects neurons. We hypothesize (a) that cPLA2a activity enhances stroke injury by amplifying inflammation;(b) that levels of both cPLA2a and KIDS- cPLA2a are increased following cerebral ischemia/reperfusion, (c) that the balance between cPLA2a and KIDS- cPLA2a influences cell fate in the hippocampus following ischemia/reperfusion. Aim 1 will test if cPLA2a knockouts or mice treated with specific cPLA2a inhibitors have decreased infarct size, altered cerebral perfusion, and gene induction, as compared to controls after transient middle cerebral artery occlusion. Results will also define a therapeutic time window for cPLA2a inhibition. Aim 2 will correlate the cerebral induction of cPLA2at eicosanoid synthesis, and markers of inflammation following ischemia using sensitive molecular, immunohistochemical and biochemical assays developed in our labs. Sensitive mass spectrometry will identify cPLA2a-dependent lipid mediators of ischemia/reperfusion injury. Aim 3 will test if cPLA2a and KIDS- cPLA2a are induced in the hippocampus following transient global ischemia and measure molecular and behavioral outcomes in mice. Further examination in hippocampal neurons in culture and in organotypic slice culture will be performed using lentivirus vectors created in our lab. Stroke injury is a major public health problem because of the limited effectiveness of treatments. The results of these studies will show if drugs aimed against the enzyme cPLA2a can be used to decrease injury following stroke and if the new protein, KIDS- cPLA2a has potential as a new brain-specific therapy for stroke.